Static electricity is commonly defined as an electrical charge resulting from the imbalance of electrons on the surface of a material. Most people are quite familiar with the everyday effects of static electricity—it is the shock one receives when touching a doorknob after walking across a carpet. The technical name for the electrical shock just described is electrostatic discharge. ESD is technically described as the transfer of electrical charge between bodies—for instance, a human hand and a doorknob—that are at different electrical potentials.
In most everyday situations, ESD can be a bother but rarely a problem. However, the problems resulting from ESD are magnified in industrial settings, where ESD is a major concern. Among the many problems that static discharge can cause are the unintentional ignition of flammable materials, damage to electronic components and systems, and the attraction of contaminants such as charged dust particles in clean room environments. Even centuries ago military forces were aware that ESD could cause the unintentional ignition of black powder. To alleviate this sometimes-catastrophic problem, ESD control measures were used as early as the 14th century to protect black powder stores. Today, many industries—from high tech manufacturing plants to businesses commonly thought of as “smoke stack” industries—are concerned with ESD and its control, since controlling ESD can lead to a safer work environment and reduction or elimination of damage resulting from ESD.
While nearly all industries are or should be concerned with controlling ESD, the concern is most acutely felt by businesses in the electronics industry. To give just a few examples of the damage that ESD can cause in the electronics industry, it can destroy or degrade semiconductor devices by changing operational characteristics. It can cause disruptions to the normal operation of an electronic system—sometimes leading to equipment failure, and in clean rooms it can cause charged particles to adhere tightly to the surface of a silicon wafer, resulting in distinct problems with wafer production and efficiency.
Given these problems and the economic damage that can result from them, control of ESD is a major concern and a complete industry has grown up around the field of ESD control.
A critical component of an ESD control program is dissipating and neutralizing ESD during handling, transporting and storing of ESD sensitive materials.
Some very common ESD protective measures are to use conductive floors, benches, bench and floor mats, wrist straps, containers, storage shelves, and transport carts all connected to a common electrical ground to reduce any build-up of electrical potential between objects or people, thereby reducing the risk of an ESD event. In addition, there are several known ESD grounding devices that are commonly used—some of these are described below and shown in the drawings.